Shrink packaging is one example of flexible packaging, and is the process of wrapping a sleeve of flexible material, called a shrink sleeve, typically cylindrical, onto a three-dimensional typically solid object such as a bottle, a food item, several cans, and so forth, and then shrinking the material over the solid object. Graphics are typically printed on the sleeve prior to the shrinking. Shrink packaging is also called shrink-sleeve packaging.
Other forms of flexible packaging include flexible, elastic foils that are tightly wrapped around a solid material. While the description herein is mostly for the case of shrink sleeve packaging, the invention is also applicable to other forms of packaging where the printed substrate is locally shrunk or stretched.
FIG. 1 shows a typical workflow for producing shrink packaging. While FIG. 1 in general is prior art, when one or more of the processes shown in FIG. 1 include one or more elements of the present invention, not all elements of FIG. 1 are prior art.
One or more original graphic elements 101, e.g., from graphics files, are used to produce 102 press-ready graphics 103, e.g., a graphics file for printing onto a rectangular sheet of the material to be used in the wrapping, e.g., to be shrunk. The press-ready graphics 103 include the graphic elements 101 positioned as desired. The press-ready graphics 103 is aligned 104 then printed and cut into the sheet to form what is called herein a foldout sleeve 105. The foldout sleeve 105 is typically in the form of a rectangular sheet with the graphics printed thereon. There are two edges that are to be joined to form a generalized cylinder, that is, a tubular object whose cross-section is not necessarily circular, and may, for example, even be close to rectangular. These edges to be joined are called the seam edges, and also the seam lines herein. The foldout sleeve is joined 106 at the seam edges to form a seam, so that the foldout sleeve thus forms a cylinder, called the unshrunk sleeve 107 in the case of shrink packaging. While not shown here, the seams may actually overlap in an actual shrink packaging process. The unshrunk sleeve is therefore a shrink sleeve prior to the shrinking process. The unshrunk sleeve 107 (a generalized cylinder) is placed 108 over a 3D object 109, called the solid object herein. The combination 111 of the unshrunk sleeve 107 and the solid object 109 is passed through a process 112, e.g., an environment and process called a shrink tunnel that applies heat in one or more ways to shrink the unshrunk sleeve to form the shrink packaging 113 around the solid object 109
Note that the above description is provided for the purpose of describing the steps taken. The order of actions as described here may be, and in many actual production systems is different. The graphics are often printed on a rotation press, resulting in an almost endless chain of foldout sleeves. Then this chain is either seamed into a long cylinder, cut into single sleeves and placed over the solid object, or it is wrapped around the object, then cut and seamed.
When the unshrunk sleeve is shrunk, the graphics typically deform. Therefore, in the process 102 of preparing the press-ready graphics 103, an operator may manually pre-distort the graphic elements to compensate for the distortion that occurs during the shrinking process 112. By manually is meant manipulating the graphic elements on a computer. This is typically carried out by a trial and error process, with a series of pre-distortions. Such trial and error multi-step processing can be expensive. Thus there is a need in the art for tools to help this process of pre-distorting.
While the workflow description above is for shrink wrapping, those in the art will know that the features described can be readily generalized to the production of any curved surface carrying graphics, where the graphics are printed on a preform that is then shaped into a curved surface by means of a shaping process. The shaping process stretches and/or shrinks the printed substrate, and in the process, distorts the graphics that were printed on it. Production processes that fall under this more general description may include flexible sleeves that are tightly wrapped around an object and plastic or metal containers that are manufactured by embossing, blow molding, thermoforming or vacuum forming. Therefore, in a more general case, the original graphics 101 are used to produce the press ready graphics 103. The graphics are printed on a substrate and shaped into a preform, or in some embodiments, the graphics are printed directly onto the preform. The preform undergoes a shaping process to produce the final curved surface with the graphics printed thereon. The shaping process typically distorts the graphics. So in the process 102 of preparing the press-ready graphics 103, an operator may pre-distort the graphic elements as described in the previous paragraph.
In creating the various electronic files, a graphics artist is concerned with the producing and placing of the various graphic elements to produce the press-ready graphics 103.
It can be very challenging to design and print graphics on a substrate to ensure that after the unshrunk sleeve is shrunk, that the various graphic images will have been printed with proper orientation, sizing, good registration, and no or little perceptible distortion viewable after the shrinking. Designing and creating such graphics is both labor intensive and very prone to error
It is for example difficult to visualize how the graphic elements will become distorted. It further is difficult to know how best to pre-distort the graphic elements in the producing of the press-ready graphics. It would be advantageous to be able to use a 3D model of the solid object and a physical model of the process of shrinking to automatically pre-distort the image. It also would be advantageous to be able to view in a 3D rendering how such pre-distorted graphics would appear after the shrinking.
Prior art approval processes for shrink packaging may be relatively costly. One such preview process includes physically printing a single copy of the packaging and shrinking it around an actual solid object, or prototype thereof, in a real shrink tunnel or by applying heat in another way.
There is a need in the art for a method that provides for previewing press-ready graphics rendered on the final 3D shape of the shrunk sleeve, e.g., to communicate intermediate results for discussion or approval.
Furthermore, there is a need in the art for a method and apparatus that can aid a designer in seeing where in an area to be printed there is likely to be deformation.